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OK, I promise that this is not another "Why can't I get the rated range on my Model 3?" question. I'm just trying to figure out how the EPA rated range matches up with the EPA's MPGe and kWh/mile ratings

Looking at the EPA ratings on fueleconomy.gov for the Model 3 AWD, Performance and Standard Range+ I find these stats:

Model 3 Performance and AWD (same stats):
  • 116 MPGe
  • 29 kWh/100 miles
  • 310 miles range
So we know that the Long Range Model 3 (RWD, AWD and Performance) all have the same 75 kWh pack, right? So if a car has a 75 kWh battery pack and the EPA rating says that the car uses 29 kWh to go 100 miles, then you divide 75 by 29 and multiply by 100 to see the actual range, right? 75/29*100. That's 258.62 miles.

In order to get 310 miles of range out of a 75 kWh pack, you actually need to have a car with an efficiency rating of 24.2 kWH/100 mile (242 Wh/mile). And I believe that is where Tesla is getting its "310 mile range" spec.

I know that it is *possible* to get 242 wH/mile out of a Model 3 LR AWD or LR AWD/P but real world numbers tend to be a bit less efficient than that. But real world vs. theoretical discussions aside, how can the EPA rating for fuel efficiency on the Model 3 AWD be 29 kWh/100 miles and yet the rated range be 310 miles? The numbers don't seem to add up.

Is my math wrong?

Screen cap of EPA ratings attached.

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There are a lot of nuances to the numbers you've listed above, but fundamentally, the 116 MPGe and 29 kWh/100mi numbers are wall-to-wheel efficiencies that include losses from the charger.
Relevant when calculating actual cost of ownership, but not when doing this math. The net charging losses don't apply to the actual battery capacity. The battery capacity of 75 kWh is a fixed number. If it takes 80 kWH of electricity to give the battery 75kWH of charge, that's useful information, but the battery's 75kWh of capacity is fixed, not variable.

And if the EPA MPGe or kwH/100 mile numbers are net of charging loss, then they are smaller than what the gross numbers would be. Bottom line is that this doesn't explain the discrepancy in the range and efficiency numbers. Both are based on EPA specs, so they should match. Unless I'm missing something.
 

Zoomit

Active Member
Sep 1, 2015
2,305
4,553
SoCal
Relevant when calculating actual cost of ownership, but not when doing this math. The net charging losses don't apply to the actual battery capacity. The battery capacity of 75 kWh is a fixed number. If it takes 80 kWH of electricity to give the battery 75kWH of charge, that's useful information, but the battery's 75kWh of capacity is fixed, not variable.

And if the EPA MPGe or kwH/100 mile numbers are net of charging loss, then they are smaller than what the gross numbers would be. Bottom line is that this doesn't explain the discrepancy in the range and efficiency numbers. Both are based on EPA specs, so they should match. Unless I'm missing something.
I don't understand your question. Try me again.

These might be helpful if you're curious about the details.
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=46585&flag=1
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=46969&flag=1
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=46584&flag=1
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=46968&flag=1
 
Just one not totally relevant comment.... How do you know the capacity is 75kWh? I don't think that is actually spec'd anywhere. And now throw the wrench in about the range being changed to 325 miles, haha. Ok so that was a question, and then a comment.
I believe it was only the Long Range RWD that got a rated range boost from 310 to 325 miles. Model 3 AWD and AWD Performance are still rated at 310 miles. At least mine still says that when I charge it to 100% and the web site states the same thing.

As for the battery being at or near 75 kWH in capacity, that came from a source that you may or may not consider reliable. A tweet from Elon. Fred Lambert wrote about it a while back:

Tesla Model 3 battery packs have capacities of ~50 kWh and ~75 kWh, says Elon Musk

Various user tests estimate the battery capacity on the LR Model 3 at anywhere from 72 to 78 kWh but I'd say only Tesla knows for sure, and they're not publicly revealing those details. Technically, Tesla can put whatever size battery in there it wants (as long as it meets its specs), and may have actually changed it since the Model 3 was launched, but that seems a bit unlikely.

I'm just saying that the EPA estimate for the Model 3 is that it uses 29 kWh to go 100 miles. If that is "accurate," then it would take 89.9 kWh of battery capacity to go 310 miles. Math.
 

Clear as mud. Thanks! :) Seriously, thanks for links to the detailed documents - fascinating stuff - but they don't explain the discrepancy.

I'm doing a very simple comparison between two numbers that are both EPA approved. The EPA certified fuel economy numbers state that the Model 3 LR AWD and AWD Performance use an estimated 29 kWH to travel 100 miles. At that rate, the battery would need to have 89.9 kWH of capacity to travel 310 miles. The Model 3 LR uses a battery that has approximately 75 kWh of capacity. Wouldn't it need to have 20% more battery capacity to reach 310 miles, based on the EPA kWh/mile estimate?

How do you reconcile these conflicting numbers?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
14,909
19,256
San Diego
OK, I promise that this is not another "Why can't I get the rated range on my Model 3?" question. I'm just trying to figure out how the EPA rated range matches up with the EPA's MPGe and kWh/mile ratings

Looking at the EPA ratings on fueleconomy.gov for the Model 3 AWD, Performance and Standard Range+ I find these stats:

Model 3 Performance and AWD (same stats):
  • 116 MPGe
  • 29 kWh/100 miles
  • 310 miles range
So we know that the Long Range Model 3 (RWD, AWD and Performance) all have the same 75 kWh pack, right? So if a car has a 75 kWh battery pack and the EPA rating says that the car uses 29 kWh to go 100 miles, then you divide 75 by 29 and multiply by 100 to see the actual range, right? 75/29*100. That's 258.62 miles.

In order to get 310 miles of range out of a 75 kWh pack, you actually need to have a car with an efficiency rating of 24.2 kWH/100 mile (242 Wh/mile). And I believe that is where Tesla is getting its "310 mile range" spec.

I know that it is *possible* to get 242 wH/mile out of a Model 3 LR AWD or LR AWD/P but real world numbers tend to be a bit less efficient than that. But real world vs. theoretical discussions aside, how can the EPA rating for fuel efficiency on the Model 3 AWD be 29 kWh/100 miles and yet the rated range be 310 miles? The numbers don't seem to add up.

Is my math wrong?

Screen cap of EPA ratings attached.

full

@Zoomit ‘s first response mostly answered your question. As he said, it is complicated. Below is an incomplete answer.

116MPGe/(33.7kWh/Ge) = 3.44mi/kWh
3.44mi/kWh => 29.05kWh/100mi

Try 29.05*0.884 = 25.69kWh/100 miles. This is the energy from the battery. The documents linked above show the actual charging efficiency (draw from battery and draw from AC mains are both given). I calculated 0.884 from page 17.

However, it still does not quite compute to the 310 using 75kWh. That is because the actual energy they were able to draw from the battery measured 79.23kWh. See document linked by @Zoomit.

79.23kWh / (25.69kWh/100mi) = 308 mi.

Note that battery is well and truly empty at that point; best not to try at home.

That is pretty close and captures most of the issues I think.

However, this is not EXACTLY how they arrived at the number I don’t think (otherwise it would be 310).

There is perhaps a little more complexity with drive cycles, scaling factor of 0.7, etc. It is not 100% explained in the documents, but with some knowledge of the calculations it might be possible to determine exactly how they do it - I think various people like @Troy know exactly how it works.

https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=35113&flag=1

You can see the raw data and the 0.7 factor application in the documents linked above. Why that 0.7 works reasonably well, I don’t know and won’t dig into further.

Hopefully the two points above mostly answer the question: 1) EPA sticker includes charging losses and 2) There is more than 75kWh available in the battery if you drain it completely.

Note that the vehicle is charged and then left overnight, so if they complied with that method, only a small component of normal vampire drain is included (but a small amount is!). Probably just 5-10% of what most typical users see. Since most users spend about 3% of their time driving, but the drive cycle the EPA uses probably spends 25-35% of the time driving. So at least 90% of the vampire losses are uncounted.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
14,909
19,256
San Diego
Relevant when calculating actual cost of ownership, but not when doing this math.

The EPA numbers are intended to capture cost of ownership (fueling). Not the battery-to-wheels efficiency.

And if the EPA MPGe or kwH/100 mile numbers are net of charging loss

The EPA numbers account for (include) charging losses.
 
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@Zoomit ‘s first response mostly answered your question. As he said, it is complicated. Below is an incomplete answer.
Actually that was pretty comprehensive. Thanks. I misinterpreted Zoomit's "include losses from the charger" to have the opposite meaning. He didn't write it wrong. I read it wrong. :)

So thanks to all of you guys for the explanation. I get it now (mostly). :)
 
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And BTW, 242 wH/mi is *EASY* to get.
Maybe on the RWD which is more efficient than the Performance AWD. But 242 wH/mile isn't easy to attain on the Performance AWD Model 3, particularly with the stock 20-inch wheels, and certainly not if you like taking advantage of the car's amazing acceleration.

I've got the 18-inch aeros on mine, but still don't normally come close to 242. Looking at my past few months of use in the SmartCharge NY dashboard, my best month so far has been 294.1 wH/mile. My monthly average is usually over 300. I'm pretty sure the SmartCharge dashboard, like the EPA stat, calculates the efficiency based on power drawn from the utility, not based on power drained from the battery. And, in my case, the vampire drain is a significant percentage of overall power usage as I don't actually drive the car very much.

BTW, for anyone in NYC or Westchester (anyone in the ConEd service area), the SmartCharge NY program is pretty cool. With it, you get a flat 10 cents back per kWh used to charge your EV, as long as you charge it off-peak. It works by plugging a dongle into the Model 3's service port then it communicates charging details and other data back to the program using a built-in cellular data connection. In addition to the rewards, you get access to a dashboard that shows charging details, efficiency and other stats. You can read more about it (including a sample dashboard) here:

Saving Money On Tesla Model 3 Charging With SmartCharge NY — A Hands-On Review | CleanTechnica
 
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My commute to work is about 16 miles each way, mostly back roads, 35-45 mph, some stop and go traffic, and Friday when I checked/watch, I got 188 Wh/mi, could have been all the things fell into place just right, with no hard acceleration, but I would easily be able to get under 250 Wh/mi daily.
 
My commute to work is about 16 miles each way, mostly back roads, 35-45 mph, some stop and go traffic, and Friday when I checked/watch, I got 188 Wh/mi, could have been all the things fell into place just right, with no hard acceleration, but I would easily be able to get under 250 Wh/mi daily.
That's pretty incredible efficiency for AWD. Is your commute downhill in both directions? :)

And do you have the 18 inch wheels with the aero caps? They do add up to about 5-7% gain in efficiency from what I've read.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
14,909
19,256
San Diego
've got the 18-inch aeros on mine, but still don't normally come close to 242. Looking at my past few months of use in the SmartCharge NY dashboard, my best month so far has been 294.1 wH/mile.

This isn't too bad; sounds like your driving efficiency is likely below 250Wh/mi if you only have to add 294Wh/mi.
 
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That's pretty incredible efficiency for AWD. Is your commute downhill in both directions? :)

And do you have the 18 inch wheels with the aero caps? They do add up to about 5-7% gain in efficiency from what I've read.
No sir, 19's.

There's a little bit of downhill, but there's about the same amount of uphill as well. I usually keep it on Chill mode so I'm not tempted to have too much fun, at least not on my daily commute. Haha
 
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This isn't too bad; sounds like your driving efficiency is likely below 250Wh/mi if you only have to add 294Wh/mi.
That was a good month as I drove the car more and had a couple of long distance road trips (800 miles each way). I know BEVs do better overall with city driving vs. highway but not when every red light is an opportunity to impress more ICE drivers to want an EV. :)

I'm a true EVangelist. The more people saying, "holy crap, how did he get that far away so quickly?" the more people will change their perception about EVs.
 

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